Second coil, why?

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pequeajim
Class G
Posts: 24
Joined: Tue Feb 20, 2007 10:10 pm
Location: New Holland, PA

Second coil, why?

Post by pequeajim »

I am going to use a Composite Design power panel in the Lightning that I am building. This has a split power toggle switch on it (master/alternator). The panel wants to see power from a battery solonoid (like a Cessna), and not wired direct.

My engine is a Jabiru 3300 and most of the aircraft built by the Jabiru USA guys just takes power directly off the battery to a 25-35 amp master breaker switch. Based on this, I have a couple of questions:


Why does Cessna use the extra solenoid?

Why do the Jabiru guys use a breaker switch and not the extra coil like the Cessna guys? Is there an advantage of one over the other?

Thanks ahead of time for the help...

weezbad
Class C
Posts: 528
Joined: Sun Oct 21, 2007 9:00 pm
Location: darlington s.c.

Post by weezbad »

well my first toughts would be, to be able to get the power shut off in the unlikely event of an electrical short. i can turn off the master relay and alt field then no electrical at all in the plane. the master relay is energized by controlling the ground side of the circuit through the master switch. with the 35 amp breaker inside and no master relay you have a 8 ga. wire unfused in the cockpit.

now i havent thought about this much so i hope there are not too many holes in my hypothesis. :oops:
william....don't let it beat you down, you are stronger than you think.

pequeajim
Class G
Posts: 24
Joined: Tue Feb 20, 2007 10:10 pm
Location: New Holland, PA

Post by pequeajim »

Good thoughts. SOmeone else told me that the main reason was to have the big stuff one the other side of teh firewall. Makes good sense. I'm going to order the following relay tomorrow...

http://www.aircraftspruce.com/catalog/e ... rrelay.php

Jim!

weezbad
Class C
Posts: 528
Joined: Sun Oct 21, 2007 9:00 pm
Location: darlington s.c.

Post by weezbad »

looks good. i think vans uses a ford relay. however i am not sure about that...as far as the starter it has a relay to but the same applies there, they dont want a #2 wire there hot at all times and this is a good thing incase the starter solenoid sticks. three relay/solenoid to get power to the starter.
william....don't let it beat you down, you are stronger than you think.

pequeajim
Class G
Posts: 24
Joined: Tue Feb 20, 2007 10:10 pm
Location: New Holland, PA

Post by pequeajim »

Thanks Bill...

weezbad
Class C
Posts: 528
Joined: Sun Oct 21, 2007 9:00 pm
Location: darlington s.c.

Post by weezbad »

anytime pal
william....don't let it beat you down, you are stronger than you think.

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